Conscience in Buddhism

According to the conscience once karma decides, as Lord Buddha sermon..When someone does a good or bad deed,it'll keep in his/her mind,Here Conscience gives the decision whether it's good or bad before keep it in once mind..anyone can lie or show this's correct/wrong..But conscience know the reality,anyone can't cheat his own conscience..

The karma gathered like this gives result when suitable time comes,So we can tell that so called conscience is also a part of our mind which decides whether our acts are good deeds or sins

Offcourse conscience plays a vital role in the enlightenment. Following quote from this sutta explains how :

At that time, the World Honored One addressed the bhikṣus: “If a bhikṣu has no shame, has no conscience, that will be detrimental to his love and reverence. If he has no love or reverence, that will be detrimental to his faith. If he has no faith, that will be detrimental to right thinking. If he does not have right thinking, that will be detrimental to his right mindfulness and right knowledge. If he does not have right mindfulness and right knowledge, that will be detrimental to guarding his faculties and guarding the precepts, to non-regret, to encouragement, to ease, to calm, to happiness, to concentration, to seeing according to reality and knowing according to reality, to disenchantment, to desirelessness, and to liberation. If he does not have liberation, that will be detrimental to having Nirvāṇa.

I think it's understood as:

• Compassion -- e.g. "all fear death: so, putting yourself in the place of another, do not kill"
• Duty -- giving their due to parents and teachers, family, employers and employees, friends
• Karmic results -- knowing that doing bad things, doing things with bad intentions, has bad results (not exactly as a punishment but just as a natural consequence, a law of nature)
• Spiritual (or, in Buddhism, mental) development -- becoming less selfish, maybe less greedy
• Presence or absence of "regret" or remorse (kukkucca or vippaṭisāra) -- an absence of remorse is not just an end in itself (because it's unpleasant to experience), but a necessary prerequisite to joy, tranquillity, concentration (AN 11.1).
• Mindfulness -- i.e. remembering what you're supposed to remember

The concerns or topic of conscience might therefore span all three parts of the threefold training -- i.e. "virtue", but also "concentration" and "wisdom".

Conscience or decision making falls under Sankhara(mental formation) aspect of an experience(an instance of the five aggregates). It is accompanied by Vinnana(consciousness). Conscience is caused, impermanent and non-self; same as the rest of the five aggregates.

Yes, conscience is known in Buddhism as "hiri-ottappa" (literally "shame-disgrace", used as one word) and plays a fairly important role, especially in the early stages of the Path as well as for lay people.

Bhikkhu Bodhi explains:

Hiri is an innate sense of shame over moral transgression; ottappa is moral dread, fear of the results of wrongdoing

Hiri, the sense of shame, has an internal reference; it is rooted in self-respect and induces us to shrink from wrongdoing out of a feeling of personal honor. Ottappa, fear of wrongdoing, has an external orientation. It is the voice of conscience that warns us of the dire consequences of moral transgression: blame and punishment by others, the painful kammic results of evil deeds, the impediment to our desire for liberation from suffering. Acariya Buddhaghosa illustrates the difference between the two with the simile of an iron rod smeared with excrement at one end and heated to a glow at the other end: hiri is like one's disgust at grabbing the rod in the place where it is smeared with excrement, ottappa is like one's fear of grabbing it in the place where it is red hot.

You can read more about this in The Guardians of the World article by Bhikkhu Bodhi.

In Mahayana abhidharma, we speak of the two mental factors that I would think are quiet similar to the "moral conscience" that you allude to. These two might be the same as 'shame' and 'conscience' in MA45. The two are:

1. Shame (Tib. ngo tsha shes pa)
2. Embarass*m*nt (Tib. khrel yod pa)

Regarding shame, the Compendium of Knowledge says:

Question: What is shame?

Answer: It is an avoidance of misdeeds on account of oneself. It has the function of acting as a support for effective restraint from misconduct.

An example of shame is to restrain from stealing even when nobody would have known. It is akin to self-respect.

Regarding embarrassment, the Compendium of Knowledge says:

Question: What is embarrassment?

Answer: It is an avoidance of misdeeds on account of others. It has the function of just that [i.e., acting as a support for effective restraint from misconduct].

An example of embarrassment is to restrain from stealing by thinking "there is a camera", paying heed to what others would think of our negativity, or thinking "what would my teacher think if he knew?".